`P=(1/(a-1)+(3sqrta+5)/(asqrta-a-sqrta+1))[((sqrta+1)^2)/(4sqrta)-1](a>0,a ne 1)`
`P=((sqrta-1)/((a-1)(sqrta-1))+(3sqrta+5)/(a(sqrta-1)-(sqrta-1))[(a+2sqrta+1)/(4sqrta)-1]`
`P=((sqrta-1+3sqrta+5)/((a-1)(sqrta-1)))[(a+2sqrta+1-4sqrta)/(4sqrta)]`
`P=((4sqrta+4)/((sqrta-1)(sqrta+1)(sqrta-1)))*(a-2sqrta+1)/(4sqrta)`
`P=(4(sqrta+1))/((sqrta-1)^2(sqrta+1))*(sqrta-1)^2/(4sqrta)`
`P=1/sqrta`
`Q=(a-sqrta+1).P`
`Q=(a-sqrta+1)/sqrta`
`Q=a/sqrta-sqrta/sqrta+1/sqrta`
`Q=sqrta-1+1/sqrta`
Áp dụng cosi
`=>sqrta+1/sqrta>=2sqrt{sqrta*1/sqrta}=2`
`=>Q>=2-1=1`
Dấu "=" `<=>sqrta=1/sqrta<=>a=1(ktm)`
`=>Q>1`